This invention relates in general to solar energy hearing equipment and, more specifically, to a method and apparatus for manufacturing solar heater panels for use in such equipment.
Many different types of solar energy collecting systems have been devised, with a variety of means for conducting the collected heat into a working fluid. One system which has been found to be very effective is described in U.S. Pat. No. 4,011,856, assigned to the assignee of this application. The system disclosed by that patent uses solar heating panels consisting of elongated plates, each having a channel along the plate centerline into which is secured a fluid carrying tubular member. Solar radiation falling on the plates is absorbed and conducted to the tubular members, and then to a working fluid flowing through the tubular members. For efficient operation, the tubular members must be securely held in the channels, with the inner surfaces of the channels and the outer surfaces of the tubular members in tight contact for good conductive heat transfer.
Many methods and apparatuses have been developed for fastening plates or fins to tubes for use in heat exchangers or other devices. Often, tubes are welded, soldered or brazed to plates or fins. Thin walled tubes are often damaged during welding or forming operations required in these methods. Also, these methods tend to produce relatively small contact areas between plate and tube.
Sandberg, in his U.S. Pat. Nos. 2,585,043 and 2,666,981, presses tubes into shallow grooves in metal sheets, forcing the tube into the sheet to form a tube holding channel. The apparatus required to do this is complex, cumbersome and slow. Also, since this technique requires the tube to act as the sheet deforming tool, the tube is likely to be deformed, damaged or cracked during the forming operation. Even with heavy walled tubes and thin sheets there is substantial risk of damage to the tubes. The Sandberg method and apparatus is not suitable for use with a combination of thin walled tubes and thick plates of the sort used in solar heater panels.
These prior methods and apparatus for forming finned tubes are generally incapable of manufacturing solar heating panels which require the use of relatively thick fins and thin tubes with large areas of physical contact between fin and tube. Thus, there is a continuing need for improved methods and apparatuses for manufacturing solar heating panels.